title: Effects of breathing frequency and flow rate on the total inward leakage of an elastomeric half-mask donned on an advanced manikin headform.
abstract: OBJECTIVE
  The objective of this study was to investigate the effects of breathing frequency and flow rate on the total inward leakage (TIL) of an elastomeric half-mask donned on an advanced manikin headform and challenged with combustion aerosols.
  
  
  METHODS
  An elastomeric half-mask respirator equipped with P100 filters was donned on an advanced manikin headform covered with life-like soft skin and challenged with aerosols originated by burning three materials: wood, paper, and plastic (polyethylene). TIL was determined as the ratio of aerosol concentrations inside (C in) and outside (C out) of the respirator (C in/C out) measured with a nanoparticle spectrometer operating in the particle size range of 20-200nm. The testing was performed under three cyclic breathing flows [mean inspiratory flow (MIF) of 30, 55, and 85 l/min] and five breathing frequencies (10, 15, 20, 25, and 30 breaths/min). A completely randomized factorial study design was chosen with four replicates for each combination of breathing flow rate and frequency.
  
  
  RESULTS
  Particle size, MIF, and combustion material had significant (P < 0.001) effects on TIL regardless of breathing frequency. Increasing breathing flow decreased TIL. Testing with plastic aerosol produced higher mean TIL values than wood and paper aerosols. The effect of the breathing frequency was complex. When analyzed using all combustion aerosols and MIFs (pooled data), breathing frequency did not significantly (P = 0.08) affect TIL. However, once the data were stratified according to combustion aerosol and MIF, the effect of breathing frequency became significant (P < 0.05) for all MIFs challenged with wood and paper combustion aerosols, and for MIF = 30 l/min only when challenged with plastic combustion aerosol.
  
  
  CONCLUSIONS
  The effect of breathing frequency on TIL is less significant than the effects of combustion aerosol and breathing flow rate for the tested elastomeric half-mask respirator. The greatest TIL occurred when challenged with plastic aerosol at 30 l/min and at a breathing frequency of 30 breaths/min.
authors.affiliation: Center for Health-Related Aerosol Studies, Department of Environmental Health, University of Cincinnati, 3323 Eden Avenue, Cincinnati, OH 45267, USA;
authors.forename: Xinjian
authors.initials: X
authors.lastname: He
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Grinshpun
authors.forename: Tiina
authors.initials: T
authors.lastname: Reponen
authors.forename: Roy
authors.initials: R
authors.lastname: McKay
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bergman
authors.forename: Ziqing
authors.initials: Z
authors.lastname: Zhuang
mesh_terms: D000336:Aerosols / Q000032:analysis; D000395:Air Pollutants, Occupational / Q000032:analysis*; D020724:Elastomers; D004784:Environmental Monitoring / Q000379:methods; D004868:Equipment Failure; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis / Q000517:prevention & control; D008348:Manikins; D008397:Masks; D016273:Occupational Exposure / Q000517:prevention & control; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012134:Respiratory Protective Devices; D056152:Respiratory Rate; D012906:Smoke / Q000032:analysis*
chemical_list: D000336:Aerosols; D000395:Air Pollutants, Occupational; D020724:Elastomers; D052638:Particulate Matter; D012906:Smoke
keywords: breathing frequency; combustion aerosol; flow rate; half-mask; manikin; total inward leakage